1. Field of the Invention
The present invention relates to dental glass powders having well controlled chemical and morphological properties, as well as methods for producing the dental glass powders. The glass powders are preferably produced by spray pyrolysis of glass precursors to form glass particles having well-controlled chemical and physical properties. The present invention is also directed to compositions for dental filling and restoration that include the glass powders.
2. Description of Related Art
Dental filling and restoration compositions are utilized to repair and fill teeth. Such dental compositions typically include a polymerizable monomer matrix with an inorganic filler, such as a glass, dispersed throughout the matrix.
For example, dental filling compositions are described in U.S. Pat. No. 5,350,782 by Sasaki et al. Sasaki et al. disclose a dental filling composition including a polymerizable monomer and an inorganic filler. The inorganic filler (e.g., amorphous silica) includes 20 to 80 weight percent spherical particles having an average size of 1 to 5 μm and 80 to 20 weight percent spherical inorganic oxide particles having an average size of 0.05 to 1 μm. It is also disclosed that the surface of the spherical particles can be treated, such as with a silane compound.
A process for the production of barium-containing silicate dental glass powders is disclosed in U.S. Pat. No. 6,000,241 by Ranade et al. Ranade et al. disclose that these glasses can exhibit the high strength and high refractive index required for dental composites. It is taught that compositions of 50% SiO2, 8% Al2O3, 9% B2O3, and 33% BaO are particularly useful for dental compositions. The process includes atomizing a precursor to the glass and pyrolyzing the atomized precursor at a temperature within the range of 1000° C. to 1600° C., such as about 1400° C.
U.S. Pat. No. 5,609,675 by Noritake et al. discloses inorganic compositions containing 60 to 99 weight percent spherical inorganic particles having a mean particle diameter greater than 0.1 μm but not greater than 1 μm, and 1 to 40 weight percent inorganic fine particles having a mean particle diameter not greater than 0.1 μm.
U.S. Pat. No. 4,764,497 by Yuasa et al. discloses a composition including spherical particles of an amorphous composition with a particle size of 0.1 to 1 μm and a standard deviation of 1.3. Yuasa et al. do not disclose the use of larger particles, such as those greater than about 1 μm in size.
There remains a need for glass particles for dental filling and restorative compositions and improved methods for making the glass particles.